Electrochemical Oxidation of ZrN Hard (PVD) Coatings Studied by XPS
Electrochemical Oxidation of ZrN Hard (PVD) Coatings Studied by XPS
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DOI：
10.1002/(sici)1096-9918(199607)24:7
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发表时间：
1996-07
影响因子：
1.7
通讯作者：
I. Milošev;H. Strehblow;M. Gaberšček;B. Navinšek
中科院分区：
文献类型：
--
作者：
I. Milošev;H. Strehblow;M. Gaberšček;B. Navinšek
氮化锆（ZrN）属于技术上重要的一类材料，即硬质摩擦学涂层。利用x射线光电子能谱（XPS）结合极化实验和电化学交流阻抗谱研究了ZrN在邻苯二甲酸盐缓冲液（pH 5.0）中电化学氧化形成的层的组成、结构、厚度和电子性能。结果与在高温下热氧化形成的层（即ZrO2）以及在室温下空气氧化形成的层进行了比较。ZrN到ZrO2的电化学氧化是通过形成混合氮化氧/氧化物层进行的，然后在足够的正电位下转化为氧化物。角度分辨XPS测量有助于更好地了解深层地层结构。在室温下将ZrN暴露在空气中会形成一层薄薄的氮化氧/氧化层。氮化物、氧氮化物和氧化物在层内的深度分布呈逐渐变化的趋势。XPS价带谱的分析为研究材料的电子特性提供了有价值的信息。ZrN的实验价带谱与文献中理论计算的态密度图有很好的相关性。与金属导体ZrN相比，电化学氧化和空气氧化形成的层具有绝缘性能。潜水泵在循环伏安图中逐次减小的电流密度以及通过交流阻抗测量得到的电阻率值（∽1012 Ω·cm）也支持潜水泵层的绝缘特性。因此，在ZrN上形成的氧化层是稳定的，可以防止ZrN衬底进一步氧化。
Zirconium nitride (ZrN) belongs to the group of technologically important materials, namely hard tribological coatings. X-ray photoelectron spectroscopy (XPS) in combination with polarization experiments and electrochemical a.c. impedance spectroscopy has been used to study the composition, structure, thickness and electronic properties of layers formed by electrochemical oxidation of ZrN in phthalate buffer (pH 5.0). Results are compared to those obtained for layers formed by thermal oxidation at elevated temperature, i.e. ZrO2 , as well as by air oxidation at room temperature. Electrochemical oxidation of ZrN to ZrO2 proceeds via the formation of a mixed oxynitride/oxide layer, which then transforms into oxide at sufficiently positive potentials. Angle-resolved XPS measurements contribute to a better understanding of the in-depth layer structure. Exposure of ZrN to air at room temperature results in the formation of a thin oxynitride/oxide layer. The layer exhibits a gradually changing in-depth distribution of various species, i.e. nitride, oxynitride and oxide. Analysis of XPS valence band spectra offers valuable information concerning the electronic properties of investigated materials. The experimental valence band spectrum for ZrN correlates well with a theoretically calculated density-of-states diagram from the literature. In contrast to ZrN, which is a metallic conductor, layers formed by electrochemical oxidation, as well as by air oxidation, exhibit insulating properties. The insulating character of the formed layers is supported also by a decreased current density in subsequent cycles in cyclic voltammograms, as well as by the resistivity value (∽1012 Ω · cm) calculated from a.c. impedance measurements. Therefore, the oxide layer formed on ZrN is stable and prevents further oxidation of the ZrN substrate.